Thermo Fisher Scientific Orion Bromide ISE User guide

User Guide

Bromide

Ion Selective

Electrode

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IBromide Ion Selective Electrode User Guide

Table of Contents

Introduction ......................................1

Required Equipment ...............................2

Serial Dilutions ...................................3

Electrode Setup...................................4

Electrode Preparation .................................4

Checking Electrode Operation (Slope) . . . . . . . . . . . . . . . . . . . . .6

Measurement Units ...................................7

Sample Requirements .................................7

Measuring Hints......................................8

Electrode Storage.....................................9

Electrode Maintenance................................10

Analytical Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Direct Calibration Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Small Volume Direct Calibration Technique . . . . . . . . . . . . . . . . . 18

Low Level Calibration Technique . . . . . . . . . . . . . . . . . . . . . . . .22

Known Addition Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Electrode Characteristics . . . . . . . . . . . . . . . . . . . . . . . . .32

Electrode Response..................................32

Reproducibility ......................................32

Limits of Detection...................................32

Temperature Effects..................................33

Interferences .......................................34

Complexation .......................................35

Theory of Operation..................................36

Troubleshooting..................................38

Assistance .........................................39

Warranty...........................................39

Troubleshooting Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Ordering Information .............................41

Speciﬁcations ...................................42

II Bromide Ion Selective Electrode User Guide

1Bromide Ion Selective Electrode User Guide

Introduction

This user guide contains information on the preparation,

operation and maintenance for the bromide ion selective

electrode (ISE). General analytical procedures, electrode

characteristics and electrode theory are also included in this

user guide. Bromide electrodes measure free bromide ions in

aqueous solutions quickly, simply, accurately and economically.

Technical Support Chemists can be consulted for assistance

and troubleshooting advice. Within the United States call

1.800.225.1480 and outside the United States call 978.232.6000

or fax 978.232.6031. In Europe, the Middle East and Africa,

contact your local authorized dealer. For the most current

contact information, visit www.thermo.com/contactwater.

For the latest application and technical resources for Thermo

Scientiﬁc Orion products, visit www.thermo.com/waterapps.

Bromide ionplus® Sure-Flow® Solid State

Combination ISE, Cat. No. 9635BNWP

The bromide combination electrode has the sensing and

reference half-cells built into one electrode, which decreases the

amount of required solutions and reduces waste. The built-in

Sure-Flow reference junction prevents electrode clogging and

provides fast and stabile readings. The bromide combination

electrode is available with a waterproof BNC connector, Cat. No.

9635BNWP. Electrodes with a waterproof BNC connector can be

used on any ISE or mV meter with a BNC connection.

Bromide Solid State Half-Cell ISE,

Cat. No. 9435BN and 9435SC

The bromide half-cell electrode must be used with the double

junction reference electrode, Cat. No. 900200. The bromide

half-cell electrode is available with a BNC connector, Cat.

No. 9435BN, and a screw cap connector, Cat. No. 9435SC.

Electrodes with a screw cap connector require a separate cable.

2Bromide Ion Selective Electrode User Guide

Required Equipment

1. Thermo Scientiﬁc Orion ISE meter, such as the 4-Star pH/ISE

meter or 5-Star pH/ISE/DO/conductivity meter; equivalent

ISE meter; or mV meter with a 0.1 mV resolution.

Bromide electrodes can be used on any ISE or mV meter

with a BNC connection. The electrodes can also be used

on meters with a variety of inputs when an adapter cable is

used. Visit www.thermo.com/water for details.

2. Thermo Scientiﬁc Orion bromide electrode.

The 9435BN and 9435SC bromide half-cell electrodes

require a separate reference electrode, Cat. No. 900200.

3. Magnetic stirrer or Thermo Scientiﬁc Orion stirrer probe,

Cat. No. 096019. The stirrer probe can be used with 3-Star,

4-Star and 5-Star benchtop meters.

4. Volumetric ﬂasks, graduated cylinders and beakers. Plastic

labware is required for low level bromide analysis.

5. Distilled or deionized water.

6. Bromide electrode ﬁlling solution.

Use Optimum Results™ D ﬁlling solution, Cat. No. 900063,

for the 9635BNWP bromide combination electrode.

Use inner chamber ﬁlling solution, Cat. No. 900002, and

outer chamber ﬁlling solution, Cat. No. 900003, for the

double junction reference electrode that is used with the

9435BN and 9435SC bromide half-cell electrodes.

7. 0.1 M NaBr calibration standard, Cat. No. 943506.

8. Bromide ionic strength adjuster (ISA), Cat. No. 940011.

ISA provides a constant background ionic strength for

samples and standards.

3Bromide Ion Selective Electrode User Guide

Serial Dilutions

Serial dilution is the best method for the preparation of

standards. Serial dilution means that an initial standard is diluted,

using volumetric glassware, to prepare a second standard

solution. The second standard is similarly diluted to prepare a

third standard, and so on, until the desired range of standards

has been prepared.

1. To prepare a 10-2 M NaBr standard (799 ppm bromide) –

Pipet 10 mL of the 0.1 M NaBr standard into a 100 mL

volumetric ﬂask. Dilute to the mark with deionized water

and mix well.

2. To prepare a 10-3 M NaBr standard (79.9 ppm bromide) –

Pipet 10 mL of the 10-2 M NaBr standard into a 100 mL

volumetric ﬂask. Dilute to the mark with deionized water

and mix well.

3. To prepare a 10-4 M NaBr standard (7.99 ppm bromide) –

Pipet 10 mL of the 10-3 M NaBr standard into a 100 mL

volumetric ﬂask. Dilute to the mark with deionized water

and mix well.

To prepare standards with a different concentration use the

following formula:

C1 * V1 = C2 * V2

C1 = concentration of original standard

V1 = volume of original standard

C2 = concentration of standard after dilution

V2 = volume of standard after dilution

For example, to prepare 1000 mL of a 100 ppm bromide standard

from a 7990 ppm bromide standard:

C1 = 7990 ppm bromide

V1 = unknown

C2 = 100 ppm bromide

V2 = 1000 mL

7990 ppm * V1 = 100 ppm * 1000 mL

V1 = (100 ppm * 1000 mL) / 7990 ppm = 12.5 mL

4Bromide Ion Selective Electrode User Guide

Electrode Setup

Electrode Preparation

9435BN and 9435SC Bromide Half-Cell Electrode – Remove

the protective shipping cap from the sensing element and save

the cap for storage.

900200 Double Junction Reference Electrode – Prepare the

reference electrode according to the reference electrode user

guide. Fill the reference electrode with inner chamber ﬁlling

solution, Cat. No. 900002, and outer chamber ﬁlling solution,

Cat. No. 900003.

9635BNWP Bromide Combination Electrode – Remove the

protective shipping cap from the sensing element and save the

cap for storage. Fill the electrode with Optimum Results D ﬁlling

solution, Cat. No. 900063.

9635BNWP Bromide Combination Electrode

Filling Instructions

1. Lift the ﬂip spout on the ﬁlling solution bottle to a

vertical position.

2. Insert the spout into the ﬁlling hole on the outer body of the

electrode and add a small amount of ﬁlling solution to the

reference chamber. Invert the electrode to moisten the top

O-ring and then return the electrode to the upright position.

3. Hold the electrode body with one hand and use your thumb

to push down on the electrode cap to allow a few drops of

ﬁlling solution to drain out of the electrode.

4. Release the electrode cap. If the sleeve does not return

to its original position, check if the O-ring is moist and

repeat steps 2 through 4 until the sleeve returns to the

original position.

5. Add ﬁlling solution to the electrode up to the ﬁlling hole.

Note: Add ﬁlling solution each day before using the electrode.

The ﬁlling solution level should be at least one inch above the

level of sample in the beaker to ensure a proper ﬂow rate. The ﬁll

hole should always be open when taking measurements.

5Bromide Ion Selective Electrode User Guide

Figure 1

9635BNWP Bromide Combination Electrode

cap

epoxy-coated

spring

cable

O-ring

ﬁll hole

inner cone

reference

element

ﬁlling solution

chamber

inner

electrode body

outer

electrode body

6Bromide Ion Selective Electrode User Guide

Checking Electrode Operation (Slope)

These are general instructions that can be used with most

meters to check the electrode operation. Refer to the meter user

guide for more speciﬁc information.

This procedure measures electrode slope. Slope is deﬁned

as the change in millivolts observed with every tenfold change

in concentration. Obtaining the slope value provides the best

means for checking electrode operation.

1. If the electrode has been stored dry, prepare the electrode

as described in the Electrode Preparation section.

2. Connect the electrode to a meter with a mV mode. Set the

meter to the mV mode.

3. Add 100 mL of distilled water and 2 mL of ISA into a 150 mL

beaker. Stir the solution thoroughly.

4. Rinse the electrode with distilled water and place the

electrode into the solution prepared in step 3.

5. Select either a 0.1 M or 1000 ppm bromide standard. Pipet

1 mL of the standard into the beaker and stir the solution

thoroughly. When a stable reading is displayed, record the

electrode potential in millivolts.

6. Pipet 10 mL of the same standard into the same beaker

and stir the solution thoroughly. When a stable reading is

displayed, record the electrode potential in millivolts.

7. There should be a -54 to -60 mV difference between the two

millivolt readings when the solution temperature is between

20 to 25 °C. If the millivolt potential is not within this range,

refer to the Troubleshooting section.

7Bromide Ion Selective Electrode User Guide

Measurement Units

Bromide concentration can be measured in moles per liter (M),

parts per million (ppm) or any convenient concentration unit.

Table 1

Concentration Unit Conversion Factors

Moles/Liter (M) ppm

1.0 79900

10-1 7990

1.25 x 10-2 1000

10-2 799

10-3 79.9

10-4 7.99

1.25 x 10-5 1

Sample Requirements

The epoxy body of the bromide electrode is resistant to damage

by aqueous solutions. The electrode may be used intermittently

in solutions that contain methanol, benzene or acetone. Contact

Technical Support for information on using the electrode for

speciﬁc applications.

Samples and standards should be at the same temperature. A

1 °C difference in temperature for a 10-3 M bromide solution will

give rise to about a 4% error when using the half-cell bromide

electrode, Cat. No. 9435BN and 9435SC. The combination

bromide electrode, Cat. No. 9635BNWP, when used with

Optimum Results D ﬁlling solution, produces less than a 1%

error in the same solution.

The solution temperature must be less than 80 °C.

In all analytical procedures, ISA must be added to all samples and

standards before measurements are taken.

8Bromide Ion Selective Electrode User Guide

Measuring Hints

• Stir all standards and samples at a uniform, moderate rate.

Place a piece of insulating material, such as Styrofoam or

cardboard, between the magnetic stir plate and beaker to

prevent measurement errors from the transfer of heat to

the sample.

• Always use freshly prepared standards for calibration.

• Always rinse the electrode with distilled water between

measurements and shake the electrode to remove the

water and prevent sample carryover. Do not wipe or rub the

electrode sensing element.

• Allow all standards and samples to reach the same

temperature for precise measurements.

• Concentrated samples (greater than 7990 ppm or 10-1 M

bromide) should be diluted before measurement.

• Verify the electrode calibration every two hours by placing

the electrode in a fresh aliquot of the least concentrated

standard used for calibration. If the value has changed by

more than 2%, recalibrate the electrode.

• After immersing the electrode in a solution, check the

electrode sensing surface for air bubbles and remove air

bubbles by reimmersing the electrode in the solution and

gently tapping it.

• For high ionic strength samples, prepare standards with a

background composition similar to the sample.

• The ﬁll hole cover must be open during measurements to

ensure a uniform ﬂow of ﬁlling solution.

• If the combination electrode is used and the electrode is

used in dirty or viscous samples or the electrode response

becomes sluggish, empty the electrode completely, hold

the junction open and ﬂush the junction with distilled water.

Empty any water from the electrode and reﬁll it with fresh

ﬁlling solution. Press down on the electrode cap to let a few

drops of the ﬁlling solution ﬂow out of the electrode and

then replenish any lost solution.

9Bromide Ion Selective Electrode User Guide

Electrode Storage

Bromide Half-Cell Electrode Storage,

Cat. No. 9435BN and 9435SC

The bromide half-cell electrode should be rinsed thoroughly with

distilled water and stored dry in the air at all times. When storing

the electrode for long periods of time, cover the sensing element

with the protective shipping cap.

Double Junction Reference Electrode Storage,

Cat. No. 900200

The double junction reference electrode may be stored in

the outer chamber ﬁlling solution, Cat. No. 900003, between

sample measurements and up to one week. The ﬁlling solution

inside the electrode should not be allowed to evaporate, as

crystallization will result.

For storage longer than one week, drain the reference electrode,

ﬂush the inside with distilled water and store the electrode dry.

Bromide Combination Electrode Storage,

Cat. No. 9635BNWP

For storage between measurements and up to one week, store

the electrode in a 4 M potassium chloride solution with bromide.

The bromide concentration of the storage solution should be

close to the least concentrated bromide calibration standard. Do

not add ISA to the storage solution. The ﬁlling solution inside the

electrode should not be allowed to evaporate, as crystallization

will result.

For storage longer than one week, drain the electrode, ﬂush the

chamber with distilled water and store the electrode dry with the

protective shipping cap covering the sensing element.

10 Bromide Ion Selective Electrode User Guide

Electrode Maintenance

Polishing the Bromide Combination Electrode and

Bromide Half-Cell Electrode

The sensing surface of solid state electrodes can wear over time,

which causes drift, poor reproducibility and loss of response in

low level samples. The electrode can be restored by polishing

the sensing surface with a polishing strip, Cat. No. 948201. The

polishing strip can also be used if the sensing surface has been

etched or chemically poisoned.

1. Cut off about an inch of the polishing strip.

2. Hold the electrode with the sensing surface facing up.

3. Place a few drops of distilled water on the sensing surface.

4. With the frosted side of the polishing strip facing down, use

light ﬁnger pressure to place the polishing strip on top of the

sensing surface.

5. Rotate the electrode for about 30 seconds.

6. Rinse the electrode with distilled water and soak the

electrode in a 1 ppm or 10-5 M bromide standard for

ten minutes.

Bromide Combination Electrode and Double

Junction Reference Electrode Flushing

If the area between the electrode sleeve and inner cone

becomes clogged with sample or precipitate, ﬂush the area with

ﬁlling solution or distilled water.

1. Hold the electrode body with one hand and use your thumb

to push down on the electrode cap to drain the electrode.

Push down on the cap until all the ﬁlling solution is drained

from the chamber.

2. Fill the electrode with distilled water and then push down on

the cap until all the water is drained from the chamber.

3. Fill the electrode with fresh ﬁlling solution up to the ﬁll hole.

Push down on the cap to allow a few drops of ﬁlling

solution to drain out of the electrode and replenish the lost

ﬁlling solution.

11Bromide Ion Selective Electrode User Guide

Disassembling and Reassembling the Bromide

Combination Electrode

Note: Disassembly is usually not required and should not be

done unless a thorough cleaning is required.

1. Tip the electrode so the ﬁlling solution moistens the O-ring

on the electrode body. Hold the electrode body with one

hand and use your thumb to push down on the electrode

cap to drain the electrode.

2. Unscrew the cap counterclockwise and then slide the cap

and spring up the cable.

3. Hold the outer sleeve with one hand and ﬁrmly push down

on the threaded portion with your thumb and foreﬁnger to

separate the inner body from the sleeve.

4. Grasp the inner cone with a clean, lint-free tissue and

withdraw the body from the sleeve using a gentle twisting

motion. Do not touch the pellet above the cone, as it will

damage to the pellet. Rinse the outside of the electrode

body and the entire sleeve with distilled water. Allow it to

air dry.

5. Moisten the O-ring on the electrode body with a drop of

ﬁlling solution. Insert the screw-thread end of the electrode

body into the tapered, ground end of the sleeve.

6. Push the body into the sleeve using a gentle twisting motion

until the bottom surface of the inner cone is ﬂush with the

tapered end of the sleeve.

7. Place the spring onto the electrode body and screw on the

cap. Reﬁll the electrode with ﬁlling solution.

12 Bromide Ion Selective Electrode User Guide

Analytical Techniques

A variety of analytical techniques are available to the analyst. The

following is a description of these techniques.

Direct Calibration is a simple procedure for measuring a large

number of samples. Only one meter reading is required for each

sample. Calibration is performed using a series of standards.

The concentration of the samples is determined by comparison

to the standards. ISA is added to all solutions to ensure that

samples and standards have similar ionic strength.

Low Level Calibration is a similar to the direct calibration

technique. This method is recommended when the expected

sample concentration is less than 0.4 ppm or 5 x 10-6 M

bromide. A minimum three point calibration is recommended

to compensate for the electrode’s non-linear response at these

concentrations. A special calibration standard preparation

procedure is the best means of preparing low level calibration

standards.

Incremental Techniques provide a useful method for measuring

samples, since a calibration is not required. The different

incremental techniques are described below. They can be

used to measure the total concentration of a speciﬁc ion in the

presence of a large (50 to 100 times) excess of complexing

agents. As in direct calibration, any convenient concentration

unit can be used.

Known Addition is useful for measuring dilute samples,

checking the results of direct calibration (when no

complexing agents are present), or measuring the total

concentration of an ion in the presence of an excess

complexing agent. The electrode is immersed in the sample

solution and an aliquot of a standard solution containing the

measured species is added to the sample. From the change

in potential before and after the addition, the original sample

concentration is determined.

13Bromide Ion Selective Electrode User Guide

Table 2

Recommended Measuring Techniques

Direct

Calibration

Small

Volume

Direct

Calibration

Low Level

Calibration

Known

Addition

[Br-] < 0.4 ppm ✔

[Br-] > 0.4 ppm ✔ ✔

[Br-] > 1.0 ppm ✔

Occasional

Sampling ✔

Small sample

volume ✔

Large number

of samples ✔ ✔ ✔

Reduce

chemical

usage

✔

Field

measurement ✔

Ionic strength

greater than

0.1 M

✔

Complicated

background ✔

14 Bromide Ion Selective Electrode User Guide

Direct Calibration Technique

Typical Direct Calibration Curve

In the direct calibration procedure, a calibration curve is

constructed either in the meter memory or on semi-logarithmic

paper. Electrode potentials of standard solutions are measured

and plotted on the linear axis against their concentrations on the

log axis. In the linear regions of the curves, only two standards

are needed to determine a calibration curve. In non-linear

regions, more points must be taken. These direct calibration

procedures are given for concentrations in the region of linear

electrode response. Low level measurement procedures are

given in a following section for measurements in the non-linear

electrode region.

Figure 2

Typical Direct Calibration Curve

+60

+80

+100

+120

+140

+160

+180

10-6

.1 1 10 102103

Molarity

ppm Br-



10-5 10-4 10-3 10-2



+40

-40.0

-20.0

0

+20

Electrode 

potential

(mV)

-57 mV

10-fold change

15Bromide Ion Selective Electrode User Guide

Direct Calibration Overview

The following direct measurement procedures are recommended

for moderate to high level measurements. Samples must be in

the linear range of the electrode – greater than 0.4 ppm or

5 x 10-6 M bromide. A two point calibration is sufﬁcient,

although more points can be used. When using an ISE meter,

sample concentrations can be read directly from the meter.

When using a mV meter, a calibration curve can be prepared

on semi-logarithmic graph paper, or a linear regression (against

logarithmic concentration values) can be performed using a

spreadsheet or graphing program.

Calibration Hints

• Standard concentrations should bracket the expected

sample concentrations.

• Always add 2 mL of ISA, Cat. No. 940011, per 100 mL of

standard or sample.

• For high ionic strength samples that have an ionic strength

of 0.1 M or greater, prepare standards with a background

composition similar to that of the samples, or measure the

samples using the known addition method.

• During calibration, measure the least concentrated standard

ﬁrst, and work up to the most concentrated standard.

Direct Calibration Setup

1. Prepare the electrode as described in the Electrode

Preparation section. If using the 9635BNWP combination

bromide electrode, ﬁll the electrode with Cat. No. 900063.

If using the 9435BN or 9435SC half-cell bromide electrode

with the 900200 reference electrode, ﬁll the reference

electrode with inner chamber ﬁlling solution, Cat. No.

900002, and outer chamber ﬁlling solution, Cat. No. 900003.

2. Connect the electrode to the meter.

3. Prepare at least two standards that bracket the expected

sample range and differ in concentration by a factor of ten.

Standards can be prepared in any concentration unit to suit

the particular analysis requirement. See the Serial Dilution

section for instructions on how to prepare standards. All

standards should be at the same temperature as the

samples. For details on temperature effects on electrode

performance, refer to the Temperature Effects section.

16 Bromide Ion Selective Electrode User Guide

Direct Calibration Procedure Using a

Meter with an ISE Mode

Note: See the meter user guide for more speciﬁc information.

1. Add 100 mL of the less concentrated standard and 2 mL of

ISA to a 150 mL beaker and stir the solution thoroughly.

2. Rinse the electrode with distilled water, blot it dry and place

it into the beaker with the less concentrated standard. Wait

for a stable reading and adjust the meter to display the value

of the standard, as described in the meter user guide.

3. Add 100 mL of the more concentrated standard and 2 mL

of ISA to a second 150 mL beaker and stir the solution

thoroughly.

4. Rinse the electrode with distilled water, blot it dry and place

it into the beaker with the more concentrated standard.

Wait for a stable reading and adjust the meter to display the

value of the second standard, as described in the meter user

guide.

5. Record the resulting slope value. The slope should be

between -54 and -60 mV when the standards are between

20 and 25 °C.

6. Add 100 mL of sample and 2 mL of ISA to a clean 150 mL

beaker and stir the solution thoroughly.

7. Rinse the electrode with distilled water, blot it dry and place

it into the sample. The concentration of the sample will be

displayed on the meter.

Note: Other solution volumes may be used, as long as the ratio

of solution to ISA remains 50:1.

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Thermo Fisher Scientific Orion Bromide ISE User guide

Thermo Fisher Scientific Orion Bromide ISE User guide

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